MONDAY, March 25 (HealthDay News) -- Cutting the number of hours that U.S. medical interns work in a single stretch may not improve patient care as had been hoped. Instead, the measure decreases interns' overall training time and may also increase patient risks, according to a new study.

New national rules introduced in 2011 reduced the continuous-duty hours of first-year resident physicians from 30 to 16 hours. This was done in the belief that shortening their continuous work hours would enable them to get more sleep and that less fatigue would reduce the number of serious medical errors made by residents.

This study found, however, that the changes did not increase the amount of sleep that interns got each week, and that there was a significant increase in the number of potentially dangerous handoffs of patients from one resident to another.

In addition, the changes led to a decline in the residents' training opportunities, such as participating in fewer beside "rounds," according to the study, which was published online March 25 in the journal JAMA Internal Medicine.

The researchers said their findings suggest the new rules may have the unintended effects of making patients less safe and compromising resident training.

"The consequences of these sweeping regulations are potentially very serious," study leader Sanjay Desai, an assistant professor of medicine at the Johns Hopkins University School of Medicine, said in a university news release.

"Despite the best of intentions, the reduced work hours are handcuffing training programs, and benefits to patient safety and trainee well-being have not been systematically demonstrated," said Desai, who is also the director of the internal medicine residency program at the Johns Hopkins Hospital.

He said the 16-hour limit was put in place without evidence of whether it would improve patient safety and outcomes, and called for further research into its impact.